The present invention relates to a new and improved method of, and apparatus for, wrapping compressible objects, especially substantially quadrangular, block-like objects, particularly packages formed by stacked, substantially flat products, for example, printed products, in a substantially web-like wrapping material.
While the description to follow, as a matter of convenience, refers to the wrapping of printed products, obviously other types of products can be conveniently handled, and therefore, the use of this term is not to be construed in a limiting sense in any way whatsoever, merely is to be viewed as an exemplary and desirable field of application for the inventive measures.
In its more particular aspects, the present invention relates specifically to a new and improved method of wrapping compressible objects, especially substantially quadrangular, block-like objects, particularly packages, formed by stacked, flat products, for example, printed products, in a web-like wrapping material or web-like foil. During a first step of such method the object to be wrapped is moved against a web or web-like foil of wrapping material which is held so as to extend transversely to the path of movement of the object. During the course of further movement of the object, the web of wrapping material is applied around the object in a substantially U-shape. During a subsequent second step of the method the web of wrapping material is withdrawn from a storage roll and guided along a rear side of the object as seen in its direction of movement.
In known wrapping machines operating according to a method of such kind, there are arranged related storage rolls holding a weldable foil above and below the path of movement of the object to be wrapped. The ends of the two foils are welded to each other so that a foil curtain is formed which extends transversely to the path of movement of the object. The object is moved towards the foil curtain and during its further course of movement entrains the foil which thus is applied to three sides of the object in a U-shape. The two foil sections which run along the top side and the bottom side of the object, respectively, are brought together on the rear side of the object while the two storage rolls are unwound and are interconnected by a severing welding action in which the two foils are welded to each other to again form a new foil curtain at the same time. The two foil sections which are to be welded to each other on the rear side of the object may not be subject to an appreciable tension during the severing and welding operation. Therefore, the wrapping or enclosure thus formed extends only relatively loosely around the object. For this reason, the enclosed object is subsequently passed through a heat tunnel in which the foil is subject to shrinkage and afterwards narrowly or tightly encloses the object.
Such apparatus has the disadvantage of a considerable structural expense and requires the use of relatively thick and weldable foils.